On Tue, 2020-02-25 at 02:42:58 +1030, Steve Langasek wrote: > On Fri, Feb 21, 2020 at 02:04:37PM -0800, Kees Cook wrote: >> On Thu, Feb 20, 2020 at 03:45:39AM +0000, Seth Arnold wrote: >> > I'm worried that turning this flag on for the first time in an LTS release >> > may be breaking too many expectations. > >> > Adapting applications may be too much effort; because I don't know what >> > exactly apport is doing here it is hard to estimate how much effort it >> > will take to adapt it. Possibly the user-launched apport instances need >> > to create their own directory on launch. Possibly apport needs a >> > more invasive redesign. >> > [...] >> > Source code searching is not practical. The combination of working >> > with files in a world-writable sticky directory and not already using >> > O_EXCL with O_CREAT is not feasible to search for. > >> FWIW, I think that the scope of the change is small enough (only in >> world-writable stick directories) and dramatic enough (usually total >> failure), that the risk is worth the benefit. Excepting the very few >> special directories (like /var/crash, where the software using them >> is likely enumerable), I would also argue that breaking stuff in >> "standard" temp directories (like /tmp) that isn't using O_EXCL is >> actually _desirable_, given that it is expressly risky to operate in >> that condition. > >> And, I would suggest that doing this in an LTS is the right thing to do, >> otherwise you wait 2 years before gaining this defense that would be >> actively _disabled_ compared to all other distros with a modern version >> of systemd. And if this is the first noticed problem, that seems to be a >> reasonably good indication of how rare the case is of it creating "real" >> problems. > > As an additional wrinkle, procps in focal-proposed is now setting > fs.protected_regular=2 by default, overriding the systemd setting. This > hasn't made it out of proposed yet because the additional restriction broke > the postgresql-common autopkgtest (fix for this is in progress): > https://bugs.launchpad.net/ubuntu/+source/procps/+bug/1864423 > > Kees, it sounds like you were advocating for setting the level to > fs.protected_regular=1, but NOT raising it to 2. Should we back out this > procps change for 20.04?
(I'll let Kees respond for himself but figured this was a good point to reply) From the Ubuntu Security team's view, it is not clear how much breakage will result from setting this to 2 - setting protected_regular=1 is already a good win and so far has seen little fallout that I know of (Apport has already worked around this), but given how close we are to FF I am a bit hesitant to mandate for this to be =2 (given we already have one known failure as a result). From a security point of view, =2 is a better default but this is not the only view that matters. So my preference would be to keep this at =2 for now but be confident that we can back it out to =1 in the event that we suddenly discover a bunch more issues in the near term. > > -- > Steve Langasek Give me a lever long enough and a Free OS > Debian Developer to set it on, and I can move the world. > Ubuntu Developer https://www.debian.org/ > slanga...@ubuntu.com vor...@debian.org -- ubuntu-devel mailing list ubuntu-devel@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-devel
